The invention relates to internal combustion engine electrostatic crankcase ventilation systems, including for diesel engines, and more particularly to the EDC, electrostatic droplet collector, in such system.
Electrostatic collectors or precipitators, including for diesel engine electrostatic crankcase ventilation systems, are known in the prior art. In its simplest form, a high voltage corona discharge electrode is placed in the center of a grounded canister or tube forming an annular ground plane providing a collector electrode around the discharge electrode. A high DC voltage, such as several thousand volts, e.g. 15 kV, on the center discharge electrode causes a corona discharge to develop near the electrode due to high electric field intensity. This creates charge carriers that cause the ionization of the gas in the gap between the high voltage electrode and the ground electrode. As the gas containing suspended particles flows through this region, the particles are electrically charged by the ions. The charged particles are then precipitated electrostatically by the electric field onto the interior surface of the collecting tube or canister.
EDCs have been used in diesel engine crankcase ventilation systems for removing suspended particulate matter including oil droplets from the blowby gas, for example so that the blowby gas can be returned to the atmosphere, or to the fresh air intake side of the diesel engine for further combustion thus providing a blowby gas recirculation system. EDCs are also used in other internal combustion engine electrostatic crankcase ventilation systems for receiving recirculation gas from the engine, and returning cleaned gas to the engine.
The corona discharge electrode assembly as commonly used in the prior art has a holder or bobbin with a 0.006 inch diameter wire strung in a diagonal direction. The bobbin is provided by a central drum extending along an axis and having a pair of annular flanges axially spaced along the drum and extending radially outwardly therefrom. The wire is a continuous member strung back and forth between the annular flanges to provide a plurality of segments supported by and extending between the annular flanges and strung axially and partially spirally diagonally between the flanges.
When the EDC is in service on a diesel engine, a build-up of sludge often occurs on the grounded electrode, i.e. the annular ground plane provided by the canister. This sludge build-up can cause a degradation of the performance of the EDC, and increases frequency of arcing. Prior solutions to this problem have focused on cleaning the assembly.
The present invention provides an EDC with a replaceable electrode assembly which is connectable and removable in a simple servicing step enabling and facilitating replacement at regular service intervals. In preferred form, part of the EDC is permanent and remains attached to the engine or an underhood mounting location, and only low cost items are replaced. The ease of servicing promotes periodic replacement, thus avoiding the noted degradation of performance. In further preferred form, the electrode assembly is replaced in a simple spin-on, spin-off step, comparable to replacing an oil filter. In one embodiment, both the collector electrode and the discharge electrode are removed as a unit from a mounting head in the system. In another embodiment, only the collector electrode is removed.